from fastapi import APIRouter, Depends, HTTPException
from sqlalchemy import select
from sqlalchemy.exc import IntegrityError
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.dependencies import get_current_user
from app.database import get_db
from app.models import Follow
from app.models.user import User
from app.schemas.schemas import FollowCreate, FollowModeUpdate, FollowSchema

router = APIRouter()

VALID_FOLLOW_TYPES = {"bill", "member", "topic"}
VALID_MODES = {"neutral", "pocket_veto", "pocket_boost"}


@router.get("", response_model=list[FollowSchema])
async def list_follows(
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    result = await db.execute(
        select(Follow)
        .where(Follow.user_id == current_user.id)
        .order_by(Follow.created_at.desc())
    )
    return result.scalars().all()


@router.post("", response_model=FollowSchema, status_code=201)
async def add_follow(
    body: FollowCreate,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    if body.follow_type not in VALID_FOLLOW_TYPES:
        raise HTTPException(status_code=400, detail=f"follow_type must be one of {VALID_FOLLOW_TYPES}")
    follow = Follow(
        user_id=current_user.id,
        follow_type=body.follow_type,
        follow_value=body.follow_value,
    )
    db.add(follow)
    try:
        await db.commit()
        await db.refresh(follow)
    except IntegrityError:
        await db.rollback()
        # Already following — return existing
        result = await db.execute(
            select(Follow).where(
                Follow.user_id == current_user.id,
                Follow.follow_type == body.follow_type,
                Follow.follow_value == body.follow_value,
            )
        )
        return result.scalar_one()
    return follow


@router.patch("/{follow_id}/mode", response_model=FollowSchema)
async def update_follow_mode(
    follow_id: int,
    body: FollowModeUpdate,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    if body.follow_mode not in VALID_MODES:
        raise HTTPException(status_code=400, detail=f"follow_mode must be one of {VALID_MODES}")
    follow = await db.get(Follow, follow_id)
    if not follow:
        raise HTTPException(status_code=404, detail="Follow not found")
    if follow.user_id != current_user.id:
        raise HTTPException(status_code=403, detail="Not your follow")
    follow.follow_mode = body.follow_mode
    await db.commit()
    await db.refresh(follow)
    return follow


@router.delete("/{follow_id}", status_code=204)
async def remove_follow(
    follow_id: int,
    db: AsyncSession = Depends(get_db),
    current_user: User = Depends(get_current_user),
):
    follow = await db.get(Follow, follow_id)
    if not follow:
        raise HTTPException(status_code=404, detail="Follow not found")
    if follow.user_id != current_user.id:
        raise HTTPException(status_code=403, detail="Not your follow")
    await db.delete(follow)
    await db.commit()